Towards understanding the microstructures and hydrocracking performance of sulfided Ni–W catalysts: Effect of metal loading

Detailed structural characterization of Ni–W hydrocracking catalysts with different metal loading were investigated before and after sulfidation by XRD, NH3-TPD, TPR, XPS and HRTEM, then their catalytic performances were examined by hydrocracking of n-dodecane. Increasing metal amount would lead to the increase in sulfidation of W phase and Ni phase, WS2 slab length and stacking WS2, the metal–support interaction became weaker and the reducibility of catalyst was improved, therefore, catalytic activity increased and reached an optimum at about 30 wt.% total metal oxides. Further increase in the metal content would lead to the multiple layer metal distribution and increasing WS2 slab length and slab stacking degree to a higher extent, which would result in the decrease of metal active site at edge and corner site of WS2 slabs, and finally decrease the catalytic activity.

Graphical abstractThe nature of the surface metal species on Ni–W based catalysts was investigated before and after sulfidation by XRD, TPR, XPS and HRTEM, and found their hydrocracking performances was determined by the microstructures of metal species.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Best catalytic activity was obtained at 30 wt.% total metal oxide with Ni / (Ni + W) = 0.5. ► Longer WS2 slabs with more stacking layers appear with excess metal loading. ► The reducibility of metal components increased with metal oxide amount. ► Catalytic activity is closely related to the nature of metal sulfide species.